A data communication speed (or a data transmission rate) of the Ethernet (registered trademark) is improved year by year, and mainstream thereof is shifting from 100 Mbps (megabit per second) to 1 Gbps (gigabit per second). A router is required to speed up a routing process than ever before. One approach to conform to the requirement is to increase a clock frequency for a CPU (Central Processing Unit) which performs a control and data processing in the router. When a clock frequency is increased, processing capacity of the CPU per unit time is improved, and as a result, capacity of the routing process is improved.
However, when the CPU operating with a high clock frequency is used, apparatus cost including the CPU becomes high. Additionally, power consumption of the apparatus becomes larger. Other than the router mentioned above, there is a multicast communication apparatus, for example, as the data processing apparatus which copies specific data as required and produces a plurality of sets of data. Usually, the data processing apparatus, such as the multicast communication apparatus or the router is used in user's premises. Therefore, such apparatuses are required to be low in price and low in power consumption. Accordingly, since the clock frequency for the CPU cannot be simply increased in the data processing apparatus, other countermeasures for improving processing capacity not relying on increasing the clock frequency are required.
Japanese Patent Application Laid-Open No. 2005-033296 discloses the multicast communication apparatus which copies user data with involvement of a CPU and performs communication by adding a header part including respective port numbers of multicast destinations to each of the user data.